Low-profile vacuum tank trailer for transporting flowable material

ABSTRACT

The present invention discloses a tank trailer for transporting flowable material. The tank trailer includes a low-profile tank having a rear section, a front section, and a transitional section. The transitional section connects the rear section and the front section such that flowable material can flow among the sections. The rear section has a rear circumference and a rear center of gravity. The front section has a front circumference and a front center of gravity. The front circumference is smaller than the rear circumference, and the rear center of gravity is lower than the front center of gravity. The sections have tops that are collinearly aligned. The front section and the transitional section are frameless underneath. The tank trailer also includes a trailer suspension operatively connected to the rear section.

TECHNICAL FIELD

The present invention relates to the field of low-profile tank trailersfor transporting fluids or other flowable materials either dry and/orliquid.

BACKGROUND ART

Many forms of tank trailers have been devised for transporting flowablematerials including liquids and a wide variety of pulverulent andgranular solid materials. One such tank trailer has a horizontallydisposed substantially cylindrical tank with upwardly inclined ends andplurality of hoppers formed in the bottom of the tank to facilitate theunloading of the tank. The tank is provided on its top with a number offiller openings for loading of the tank. The tank may also be dividedinto a number of compartments so that each compartment can be loaded andunloaded separately and independently of the other compartments. Theinclined or sloping end structure of the tanks facilitates the downwardflow of dry and liquid flowable materials when these materials are beingunloaded through the hopper bottoms. A suitable frame structure is thenattached to each end of the tank at the lower portion thereof so thatone frame structure serves as a supporting carriage for wheels and otherframe structure is provided with a trailer hitch for connecting thetrailer to a tractor.

Previously devised tank trailers are prone to roll over due to arelatively high center of gravity and a relatively narrow frame andwheel-base.

SUMMARY OF INVENTION

The present disclosure concerns low-profile tank trailers fortransporting fluids or other flowable materials either dry and/orliquid, with particular emphasis on creating a tank trailer that has areduced tendency to roll-over due to shifting cargo, imbalanced loads,cornering too quickly, or any combination of the above, including otherreasons or causes for roll-overs to occur.

The present disclosure includes low-profile tank trailers fortransporting fluids or other flowable materials either dry and/or liquidhaving a partition within a rear section of the trailer situated withinthe tank vessel directly above or proximally close to the rear axle ofthe tank trailer. The placement of this partition can create a cavitywithin the vessel where no fluid or dry material can enter. The cavitywithin the vessel may further include devices or openings that causesfluid or dry materials that errantly enter the cavity to be excised ordiscarded, whether through a pumping device, a drain, or similarmechanism. The positioning of this partition and cavity substantiallyabove the rear axle of the tank trailer provides several benefits, whichwill be detailed in the description that follows, but briefly includethe capability to of a tank trailer to carry a maximum legal loadcapacity of flowable fluid and/or dry material while maintaining a legalbridging weight distribution across the several axles of the tanktrailer and truck while simultaneously lowing the center of gravity ofthe tank trailer thereby reducing the tendency for the tank trailer toroll-over. These benefits are also achieved even when the tank traileris not at the maximum legal load capacity and/or only partially full offlowable material.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate an implementation of apparatusconsistent with the present invention and, together with the detaileddescription, serve to explain advantages and principles consistent withthe invention. In the drawings,

FIG. 1 sets forth a drawing illustrating a left perspective view of anexemplary low-profile tank trailer for transporting flowable materialaccording to embodiments of the present invention.

FIG. 2 sets forth a drawing illustrating a right orthogonal view of theexemplary low-profile tank trailer for transporting flowable materialaccording to embodiments of the present invention.

FIG. 2A sets forth a drawing illustrating a first embodiment of a firstembodiment of an exemplary partition that may be fitted within a rearportion of a low-profile tank trailer for transporting flowable materialaccording to the embodiments of the present invention.

FIG. 2B sets forth a drawing illustrating a second embodiment of anexemplary partition that may be fitted within a rear portion of alow-profile tank trailer for transporting flowable material according tothe embodiments of the present invention.

FIG. 3 sets forth a drawing illustrating a cross-section of a toporthogonal view of the frameless, self-supporting tank in the exemplarylow-profile tank trailer according to embodiments of the presentinvention at the midpoint of the tank.

FIG. 4 sets forth a drawing illustrating a right orthogonal view of theframeless, self-supporting tank in the exemplary low-profile tanktrailer according to embodiments of the present invention.

FIG. 5 sets forth a drawing illustrating a rear orthogonal view of theexemplary low-profile tank trailer according to embodiments of thepresent invention.

FIG. 6 sets forth a drawing illustrating a left perspective view ofanother exemplary low-profile tank trailer for transporting flowablematerial according to embodiments of the present invention.

FIG. 7 sets forth a drawing illustrating a right perspective view ofanother exemplary low-profile tank trailer for transporting flowablematerial according to embodiments of the present invention.

DESCRIPTION OF EMBODIMENTS

Exemplary embodiments of low-profile tank trailers for transportingflowable material are described herein with reference to theaccompanying drawings, beginning with FIG. 1. FIG. 1 sets forth adrawing illustrating a perspective view of an exemplary low-profile tanktrailer (100) for transporting flowable material according toembodiments of the present invention. A tank trailer is a semitrailerthat has a reservoir for storing flowable materials. A semi-trailer is atype of trailer that does not have a front axle. A large proportion ofweight of a semitrailer is supported by a truck, tractor, dolly, orother towing mechanism. Because a semi-trailer does not have a frontaxle, a semi-trailer is typically equipped with a landing gear (legswhich can be lowered) to support the trailer when it is uncoupled.

Flowable materials transported by a tank trailer according toembodiments of the present invention may include fluids or even solidsof a size and granularity with respect to the tank that allows thesolids, in aggregate, to take on the shape of the tank. Examples offlowable materials may include water, milk, juices, petroleum products,carbon-dioxide, nitrogen, grains, powders, gravel, or any other suchmaterials as will occur to those of skill in the art.

The low-profile tank trailer (100) of FIG. 1 includes a frameless,self-supporting tank (102). The tank (102) of FIG. 1 is an enclosedcontainer with one or more opening for adding and removing the flowablematerials. The location of such openings varies from one embodiment toanother and typically depends on the type of flowable material beingtransport by the tank trailer and the method of filling and draining thetank. When gravity is the method used to fill and drain a tank,embodiments typically having an opening at the top of the tank foradding the flowable materials, and another opening at the bottom bywhich the flowable materials are drained from the tank. In otherembodiments where a vacuum or other pump is utilized, the only openingsmay be located on the bottom of the tank, but there may be otheropenings as the top of the tank (102) for ventilation purposes. Inaddition to the openings for allowing the ingress and egress of flowablematerials, the tank (102) in the example of FIG. 1 includes threeman-hole openings along the top of the tank (102). These man-holesprovide access to the interior of the tank (102) during the fabricationprocess as well as for service and maintenance.

The tank (102) of FIG. 1 may be configured by rolling or bending sheetsof metal to form the walls of the tank (102) or by using prefabricatedmetal cylinders, tubes, or cones. Typically these metal sheets orprefabricated metal components will be welded together or fused in someother manner as will occur to those of skill in the art. Of course,other materials or methods of making tanks useful in low-profiletrailers according to embodiments of the present invention as will occurto those of skill in the art may also be useful.

The exemplary tank (102) depicted in FIG. 1 is characterized as“frameless” and “self-supporting.” The tank (102) of FIG. 1 is framelessin that the tank (102) is not structurally supported by a full framethat extends longitudinally along the full length of the tank (102).Full frames are typically implemented as beams that extend from thetrailer's suspension to the upper coupler and provide a structure onwhich to attach the tank, but other structural supports may be used toprovide other tank trailers with a full frame. The tank (102) of FIG. 1does not utilize such a full frame. Rather, the exemplary tank (102) ofFIG. 1 is structurally supported by the tank's hull, the tank's internalstructures, and by various external structures of the tank thatcircumscribe the tank's hull. Given that a full frame beneath an alreadylarge tank takes up a significant amount of space, the frameless,self-supporting nature of the exemplary tank (102) in FIG. 1 allows thetank to sit lower on the exemplary trailer (100) than traditionaltrailers that utilize a full frame underneath. This frameless,self-supporting tank configuration illustrated in FIG. 1 lowers thecenter of gravity of the entire exemplary trailer (100) with respect toother traditional trailers.

In FIG. 1, the exemplary tank (102) has a rear section (104) and a frontsection (106). The circumference of the front section (106) is smallerthan the circumference of the rear section (104). Accordingly, thediameter of the front section (106) is smaller than the diameter of therear section (104). The exemplary tank (102) of FIG. 1 also includes anintervening section (105) connecting the rear section (104) and thefront section (106). The intervening section (105) operates as atransitional section between the rear section (104) and the frontsection (106). The circumference and diameter of the transitionalsection (105) in FIG. 1 varies from the smaller circumference anddiameter of the front section (106) to the larger circumference anddiameter of the rear section (104). The transitional section (105)connects to the other sections (104, 106) such that fluid can flow amongthe sections. That is, fluids can pass from the rear section (104) tothe front section (106) through the transitional section (105) and viceversa. These exemplary sections (104, 105, 106) of FIG. 1 connecttogether along the circumference at their ends forming seams. In theexample of FIG. 1, the sections (104, 105, 106) are welded together, butother methods of fabrication may also be useful in exemplary trailersaccording to embodiments of the present invention.

In FIG. 1, the front section (106) of the tank (102) connects, through akingpin plate (116), to a truck (120) for hauling the exemplary trailer(100). The rear section (104) of the tank (102) in FIG. 1 connects to atrailer suspension (112), which in turn connects to the ground through atrailer tandem axle connected to various low-profile tires (114). Insuch a manner, the tank (102) in the example of FIG. 1 is suspendedbetween the trailer suspension (112) and the kingpin plate (116)without, as previously mentioned, the need for a full frame underneaththe length of the tank (102) for structural support. Rather, only therear section (104) has a frame and it is only a partial frame (158) thatprovides mounting surface for the trailer suspension (112). The frontsection (106) and the intervening (or transitional) section (105) ofFIG. 1, however, are frameless.

In the example of FIG. 1, the rear section (104) has an underside thatis lower than the underside of the front section (106). The underside ofthe front section (106) is sufficiently high to allow the kingpin plate(116) to be mounted underneath the front section (106) and still provideclearance for attaching the exemplary trailer (100) to a truck (120). Inthe example of FIG. 1, the underside of the rear section (104) is lowerthan the front section (106) and is situated high enough so as to permitclearance for the trailer suspension (112) and tires (114) underneath.The configuration depicted in FIG. 1 ensures that the center of gravityfor the rear section (104) is lower than the center of gravity for thefront section (106) and produces an overall center of gravity for theexemplary trailer (100) that is approximately twenty inches lower thantraditional trailers, which typically use a cylindrical tank having asingle diameter mounted above the kingpin plate.

While lowering a substantial portion of the rear section beneath thekingpin plate advantageously lowers the exemplary trailer's overallcenter of gravity, the exemplary trailer (100) of FIG. 1 is designedsuch that a portion of the tank (102) is positioned over the kingpinplate (116) via the front section (106). This configuration moves thecenter of gravity for the exemplary trailer (100) closer toward thefront of the trailer than it would otherwise be without the frontsection. The advantage of this configuration is that the weight of thefront section (106), especially when loaded, assists the exemplarytrailer (100) in bridging with the truck (120). The term “bridging”refers to the transfer of weight from the trailer onto the fifth wheelof the truck or other hauling device. Trailers in which the center ofgravity is not far enough toward the front of the trailer do not bridgewell with the truck—that is, not enough of the trailer's weight getstransferred to the fifth wheel of the truck. These trailers aredifficult and more dangerous to haul because they do not transfer enoughweight to the truck's suspension under the fifth wheel to provide goodtraction with the highway.

The exemplary trailer (100) of FIG. 1 is designed to comply with allapplicable laws and regulations concerning the use of such trailers. Inparticular, the exemplary trailer (100) is designed to ensure compliancewith the gross weight limitations promulgated by the U.S. Department ofTransportation (“DOT”) for the operation of such trailers on theInterstate Highway System. These DOT regulations require that the grossweight of a semitrailer and the truck to which it is attached not exceed80,000 pounds. Further, these DOT regulations require that the weight bedistributed across the axles in a manner not to exceed the followinglimits: 12,000 pounds for the truck's steer axle; 34,000 pounds for thetruck's tandem axles; and 34,000 pounds for the trailer's tandem axles.With the purchase of an additional endorsement, the gross weight limitmay be increased to 84,000 pounds and the limits on the weightdistribution changes as follows: 12,600 pounds for the truck's steeraxle; 35,700 pounds for the truck's tandem axles; and 35,700 pounds forthe trailer's tandem axles.

The tank (102) of the exemplary trailer (100) depicted in FIG. 1 isdesigned to carry at least 130 barrels of fluids, each barrel beingequivalent to forty-two gallons. When the tank (102) is filled to its130 barrel capacity with water, the exemplary trailer (100) and theconnected truck (120) of FIG. 1 have a gross weight that does not exceed84,000 pounds. The gross weight of the truck (120) and exemplary trailer(100) of FIG. 1 is distributed such that no more than 12,600 pounds isapplied to the truck steer axle, no more than 35,700 pounds is appliedto the truck tandem axles, and no more than 35,700 pounds is applied tothe trailer tandem axles.

These weight distribution limits place corresponding limits on thelength and diameter of the exemplary trailer (100) of FIG. 1. Forexample, the 34,000 pound limit on the trailer tandem axles limits thenumber of combinations of tank length and diameter for the rear sectionthat would allow the exemplary trailer (100) of FIG. 1 to comply withDOT regulations. The larger the diameter of the rear section (104) at aparticular length or the longer the length of the rear section (104) ata given diameter, the more weight that will shift off of the trucktandem axles onto the trailer tandem axles. Accordingly, the rearsection (104) of FIG. 1 must be sufficiently short to ensure that enoughof the tank's capacity is designed into the front section (106) and thetransitional section (105) so that the weight on the trailer's tandemaxles does not exceed 34,000 pounds. Because the front section (106) andthe transitional section (105) are smaller than the rear section (104),the overall diameter of the various sections must be sufficiently largeto contain the minimum capacity used in the industry, which in theexample of FIG. 1 is 130 barrels of fluid.

In FIG. 1, the trailer (100) includes a hose tray (166) mountedlongitudinally along a bottom, lateral portion of the rear section(104). The hose tray (166) is lower than the underside of the frontsection (106) and extends along the entire length of the rear section(104) in the example of FIG. 1. The width of the hose tray (166) of FIG.1 extends from the tank (102) outward past the tires (114) to cover thetop of the tires (114), but not so far as to make the exemplary trailer(100) wider than permissible under certain laws or regulationspromulgated by the authorities governing trailer width for trailers usedin commerce or society. Such authorities may include, for example, alocal, state, or federal government's department of transportation,public safety, highway administration, or any other such agency as willoccur to those of skill in the art. The dimensions of the hose tray(166) in FIG. 1 are for explanation only and not for limitation. One ofskill in the art will recognize that a hose tray may extend along theentire length of the rear section or may only extend along a portion ofthat length and may be configured using a variety of widths.

Because the hose tray (166) of FIG. 1 is lower than the underside of thefront section (106), the hose tray (166) of FIG. 1 considerably lowerthan the hose trays of traditional trailers. In such a manner, exemplarytrailer (100) allows a truck operator to easily access the hose tray(166) at the level of the operator's torso while standing on the ground.The configuration in the example of FIG. 1, therefore, provides moreconvenient and safer access to hoses stored on the hose tray (166) thanin traditional trailers in which the hose trays are often located at orabove the operator's head.

The exemplary trailer (100) of FIG. 1 includes a trailer suspension(112) that is operatively connected to the rear portion of the undersideof the rear section (104). The trailer suspension (112) of FIG. 1 is thesystem of cylinders, springs, shock absorbers, and/or other linkagesthat connects the trailer (100) to its axles and wheels. The trailersuspension (112) in the example of FIG. 1 is a low-ride trailersuspension. Generally, the lower that a trailer suspension allows thetank (102) of the exemplary trailer (100) to be position, the lower thecenter of gravity for the entire tank (102). Therefore, smaller trailersuspensions may be preferred provided that those smaller suspensions cansupport the weight of the exemplary trailer (100) for purposes oftransporting a full load of flowable material. For explanation only, andnot for limitation, an example of a trailer suspension useful in alow-profile tank trailer according to embodiments of the presentinvention may include the Watson & Chalin TA300 Air Ride Suspension witha 60K rating. The trailer suspension (112) of FIG. 1 connects to anaxle, which in turn, connects to a set of wheels and tires. Forexplanation only, and not for limitation, examples of an axle useful ina low-profile tank trailer according to embodiments of the presentinvention may include Watson & Chalin axles with a 25K rating, ⅝″ wall,77.5″ track, and outboard drums. Exemplary wheels and tires useful in alow-profile tank trailer according to embodiments of the presentinvention may include 10-hole steel disk hub piloted wheels and 255/70R22.5 (H) low-profile tires.

The exemplary trailer (100) of FIG. 1 is primarily made ofmetal—specifically, steel. One of ordinary skill in the art, however,will recognize that other materials may also be useful in or substitutedfor steel in low-profile tank trailers according to embodiments of thepresent invention. Such other materials may include aluminum,galvanneal, fiberglass, carbon-fiber, or any other materials as willoccur to those of skill in the art. These other materials may requiremore or less structural supports inside the tank or around thecircumference of the tank's hull depending on the overall structuralintegrity of a tank configured from these other materials.

Turning to FIG. 2 for further explanation of an exemplary low-profiletank trailer, FIG. 2 sets forth a drawing illustrating a rightorthogonal view of the exemplary low-profile tank trailer (100) fortransporting flowable material according to embodiments of the presentinvention. The low-profile tank trailer (100) of FIG. 2 includes aframeless, self-supporting tank (102) having a rear section (104), afront section (106), and an intervening section (105). The interveningsection (105) of FIG. 2 connects the rear section (104) and the frontsection (106).

FIG. 2 depicts the front section (106) having a front section underside(108) and the rear section (104) having a rear section underside (110).The front section underside (108) in FIG. 2 is higher than the rearsection underside (110), and as a corollary, the rear section underside(110) is lower than the front section underside (108). The topsides ofall the sections (104, 105, 106) in the example of FIG. 2 are alignedlongitudinally along the length of the tank (102). In this manner, thefront section (106), the transitional (or intervening) section (105),and the rear section (104) have tops that are collinearly aligned. Aspreviously mentioned, this configuration lowers the center of gravity ofthe entire trailer (100) in FIG. 2 compared to traditional trailers,typically by as much as twenty inches.

The tank (102) in the example of FIG. 2 is characterized as a“frameless, self-supporting” tank. From FIG. 2, one of skill in the artwould recognize that there is no full frame extending longitudinallyalong the tank (102) to provide structural support. Rather, thestructural support for the tank comes from the tank itself, includingthe tank's internal structures, and in the embodiment of FIG. 2, thetank's external structures around the circumference of the hull of thetank (102). While FIG. 2 depicts the use of these internal structuresand external structures around the tank's circumference, otherembodiments of the low-profile tank trailers according to embodiments ofthe present invention may not utilize such internal or externalstructures. Rather, other embodiments of the low-profile tank trailersaccording to embodiments of the present invention may rely only on thestructural support provided the tank wall itself.

Because the tank (102) in the example of FIG. 2 is frameless, the tank(102) of FIG. 2 includes a plurality of stiffener rings (130) tostructurally reinforce the tank (102). Each stiffener ring (130) in theexample of FIG. 2 is mounted along an exterior perimeter of the tank(102) at various locations aft of the front wall of the front section(106). In the example of FIG. 2, the stiffener rings (130 c, 130 d) aremounted adjacent to the seam (134 a) formed between the front section(106) and the intervening section (105) of the tank (102) to reinforcethe structural integrity of the tank (102) at that joint. Similarly, thestiffener ring (130 f) is mounted adjacent to the seam (134 b) formedbetween the intervening section (105) and the rear section (104) of thetank (102) to reinforce the structural integrity of the tank (102) atthat joint. Each of the stiffener rings (130) in the example of FIG. 2may be made from metal strips that are hard-rolled lengthwise along thesmaller edge. One of skill in the art, however, will recognize thatother materials or methods of making stiffener rings useful inlow-profile trailers according to embodiments of the present inventionmay also be useful.

In the example of FIG. 2, the tank (102) also includes two baffles(136). Each baffle (136) of FIG. 2 is mounted along an interiorperimeter of the tank (102) and spans an interior region of the tank(102). The baffles (136) in the example of FIG. 2 dampen the movement ofthe flowable material stored inside the tank (102) that typically occurswhen the low-profile tank trailer (100) is being hauled. In addition todampening the movement of the flowable materials, the baffles (136) alsoserve to reinforce the structural integrity of the tank (102). In theexample of FIG. 2, the baffle (136 a) is mounted adjacent to the seam(134 b) formed between the intervening section (105) and the rearsection (104) to reinforce the structural integrity of the tank (102) atthat joint. Each of the baffles (136) in the example of FIG. 2 may bemade from plates of metal cut to fit within the inside perimeter of thetank (102). Baffles made from such plates typically have holes or slotscut to allow the flowable material to move from one side of the bafflesto the other, thereby dampening the movement of the flowable material ascompared to the movement without such baffles. One of ordinary skill inthe art, however, will recognize that other materials or methods ofmaking baffles may also be useful in low-profile trailers according toembodiments of the present invention.

To ensure that the trailer (100) rests as low to the ground as possible,the trailer (100) of FIG. 2 includes a low-ride trailer suspension (112)operatively connected to the rear portion of the rear section underside(110). While FIG. 2 does not depict the entire trailer suspension (112),one of ordinary skill in the art will recognize that the suspensionincludes the system of cylinders, springs, shock absorbers, and/or otherlinkages that connects the exemplary trailer (100) to its axles andwheels such as, for example not limitation, the Watson & Chalin TA300Air Ride Suspension with a 60K rating. The trailer suspension (112) ofFIG. 2 connects to the rear section underside (110) through a tanksubstructure (158) mounted on top of the suspension (112). The rearsection (104) of the tank (102) in FIG. 2 is then mounted to the tanksubstructure (158). In this way, the tank substructure (158) of FIG. 2serves as an interface that bridges the underside (110) of the rearsection (104) with the trailer suspension (112).

In the example of FIG. 2, the trailer (100) also includes a plurality oflow-profile tires (114) operatively connected to the trailer suspension(112). The low-profile tires (114) connect to the trailer suspension(112) through set of axles and wheels. The low-profile nature of thetires (114) provides the trailer (100) with a lower center of gravitythan tires with larger side walls and therefore larger diameters. One ofordinary skill in the art, however, will recognize that even the use ofstandard-profile tires may still be useful in certain low-profiletrailers according to embodiments of the present invention given thatthe configuration of the frameless, self-supporting tank by itselfsufficiently lowers the center of gravity of a trailer according toembodiments of the present invention to provide greater stability andsafety than traditional trailers.

The exemplary trailer (100) of FIG. 2 includes a kingpin plate (116)connected to the front section underside (108). The kingpin plate (116)of FIG. 2 connects to the front section underside (108) through a frontsection substructure that mounts to the surface of the front sectionunderside (108) and the upper surface of the kingpin plate (116). Akingpin plate is a load bearing surface on the underside of the front ofa semitrailer. The kingpin plate typically rests on the fifth wheel of atruck, tractor, dolly, or other hauling mechanism and has adownward-protruding kingpin which is captured by the locking jaws of thefifth wheel. Another common term for a kingpin plate is an “uppercoupler.” In the example of FIG. 2, the kingpin plate (116) has akingpin (not shown) for attaching the trailer (100) to a truck (notshown). In the example of FIG. 2, a portion of the front section (106)extends in front of the kingpin plate (116) to ensure that enoughweight, when the trailer (100) is loaded, is transferred through thekingpin plate (116) to the rear truck axles for bridging purposes.

In FIG. 2, the kingpin plate (116) includes several drip holes (notshown) at a lower, rear portion of the kingpin plate (116) for expellingany liquids, such as rain or water on the road, that may accumulate inthe kingpin plate (116). These drip holes allow water or other liquidsto escape that may have accumulated inside the kingpin plate (116),which is often formed from two plates connected together with a hollowcavity there between for adding additional structural support. The dripholes may be created by drilling through the wall of the kingpin plate(116) into its inner, hollow cavity. Other methods of forming drip holesin the kingpin plate (116) as will occur to those of skill in the artmay also be useful.

In some embodiments, an exemplary trailer according to embodiments ofthe present invention may need to adjust the position of the load in thetank to assist the exemplary trailer in bridging with a truck. In suchembodiments as depicted in FIG. 2, the tank (102) may include an emptycompartment (182) that can be sealed off from the rest of the tank (102)using a partition (180). The empty compartment (182) in such embodimentsremains empty even while the remainder of the tank (102) is filled upwith the flowable material, thereby reducing the density of the rearwardregion of the tank (102). In this manner, the center of gravity for thetank (102) of FIG. 2 is shifted further toward the front of the tank(102) than it would otherwise be without the empty compartment (182).The further that the center of gravity is shifted toward the front ofthe trailer (100) of FIG. 2, the more weight from the trailer (100) willbe transferred through the kingpin plate (116) to the tractor, truck, orother hauling device.

Although in enhancing the bridging characteristics of the exemplarytrailer (100) of FIG. 2, the addition of the empty compartment mayreduce tank volume used for transporting the flowable material. If aparticular tank volume is important for an application in which thetrailer is used, the loss in tank volume may be accommodated byincreasing the circumference or the length of the tank (102) in one ormore section (104, 105, 106). Readers will note, however, thatembodiments having a partition and empty compartment are for exampleonly, not for limitation. Other embodiments of exemplary trailersaccording to the present invention may not utilize such partitions andempty compartments.

In the example of FIG. 2, the empty compartment (182) is formed by apartition (180) that separates the empty compartment (182) from the restof the tank (102). The partition (180) of FIG. 2 is mounted along aninterior perimeter of the tank (102) and spans an interior region of thetank (102). The partition (180) in the example of FIG. 2 blocks the flowof the flowable material into the empty compartment (180). In additionto sealing off the empty compartment (182), the partition (180) in theexample of FIG. 2 also serves to reinforce the structural integrity ofthe tank (102). The partition (180) in the example of FIG. 2 may be madefrom plates of metal cut to fit within the inside perimeter of the tank(102). One of ordinary skill in the art, however, will recognize thatother materials or methods of making a partition may also be useful inlow-profile trailers according to embodiments of the present invention.

In the example of FIG. 2, the empty compartment (182) is formed at therearmost portion of the tank (102) using a single partition (180) andthe tank's rear wall. One of skill in the art will recognize that thefurther rearward that the empty compartment is placed, the more that thetrailer's center of gravity will be shifted toward the front of thetrailer, thereby transferring more of the trailer's weight to tractorthrough the kingpin plate. However, the shape and placement of the emptycompartment (182) in FIG. 2 is for explanation only and not forlimitation. The empty compartment in other embodiments of the presentinvention may be implemented using multiple partitions such that theempty compartment is formed closer to the rear tandem axles of thetrailer (100). This configuration would allow the flowable material tofill up the tank on both sides of the empty compartment. The emptycompartment could be designed such that it did not extend all the way tothe bottom of the tank (102), thereby allowing the flowable material topass from one side of the empty compartment to the other. One of skillin the art will recognize other configurations for the empty compartmentthat may be useful in low-profile tank trailers according to embodimentsof the present invention.

Because the low-profile tank trailer (100) in the example of FIG. 2 doesnot have a front axle, the trailer (100) of FIG. 2 includes a landinggear (146). The landing gear (146) of FIG. 2 is composed of two jacksthat are coupled together. The landing gear is used to lift the front ofthe low-profile tank trailer (100) up so that a truck can be drivenunder the front section (104) and hitched up at the kingpin plate (116).Once hitched up, the landing gear (146) is raised to its stowed positionfor traveling.

The landing gear (146) of FIG. 2 is mounted to a junction box (144),which in turn is mounted to an underside of the intervening section(105). The junction box (144) of FIG. 2 is a container for housingelectrical connections. The junction box (144) of FIG. 2 not only servesto conceal the electrical connections from sight, but also operates todeter tampering. Although not shown, the junction box (144) of FIG. 2includes one or more drip holes at a lower, rear portion of the junctionbox (144) for expelling any liquids, such as rain or water on the roadsurface, that may accumulate in the junction box (144). Similar to thedrip holes in the kingplate, the drip holes may be created by drillingthrough the lower portion of the rear wall of the junction box (144) orthe rear portion of the bottom wall of the junction box (144) to exposethe inner cavity of the junction box (144) to the outside environment.Other methods of forming drip holes in the junction box (144) as willoccur to those of skill in the art may also be useful.

One of ordinary skill in the art will recognize that many trailers aresubject to certain laws or regulations promulgated by the authoritiesgoverning their use in commerce or society. Under such regulations,trailers are often limited to a certain maximum weight or size. Toreduce the weight of the trailer (100) in the example of FIG. 2 so thatthe exemplary trailer (100) can transport a larger quantity of flowablematerial, the rear portion of the rear section (104) has a thinner tankwall than the front portion of the rear section (104). The difference inthickness will often depend on the fabrication techniques used to createthe tank (102). For example, if the tank (102) of FIG. 2 was createdusing rolled sheets of metal of a particular thickness, the thinner rearportion of the rear section (104) could be made using sheets of metalhaving the next smaller commercially available thickness. Such thinnersheets could be used provided of course that such thinner sheets did notdiminish the structural integrity of the tank (102) of FIG. 2 beyond anacceptable level in effort reduce the weight of the exemplary trailer(100).

In the example of FIG. 2, the tank (102) extends for a length sufficientto permit the tank (102) to store an industry-standard quantity offlowable material. The industry-standard quantity represents acommercially available amount that one can typically order whenrequesting delivery of a flowable material by trailer. For example,within the industry of vacuum trailers, an industry-standard amount maybe 130 barrels. For other tank trailer industries, however, anindustry-standard quantity may be different and may be measured indifferent units. To ensure that the tank (102) of FIG. 2 providessufficient volume to store an industry-standard quantity without raisingthe center of gravity for the entire trailer (100), the rear section(104) may be designed using any industry standard diameter and thenextend longitudinally in the rear direction for a sufficient length tocreate the volume need to store an industry-standard amount. In FIG. 2,therefore, the tank volume sacrificed by raising the underside (108) ofthe front section (106) to provide clearance for the fifth-wheel of atruck is added to the rear section (104) of the tank (102) so that theexemplary trailer (100) may still be used to transport anindustry-standard quantity. One of skill in the art will recognize thatthe smaller the tank diameter that is used in the various sections ofthe tank, the longer the tank (102) of FIG. 2 must be extended in therearward direction to allow the tank to store an industry-standardquantity of flowable material. Conversely, the larger the tank diameterthat is used, the shorter the tank must be extended in the rearwarddirection to allow the tank (102) of FIG. 2 to store anindustry-standard quantity of flowable material. The larger the tankdiameter that is used, however, the higher the overall center of gravitywill be for the exemplary trailer (100) of FIG. 2.

In the example of FIG. 2, the low-profile tank trailer (100) includestwo hose trays (166) mounted longitudinally along a bottom, lateralportion (168) of the rear section (104). The hose trays (166) of FIG. 2are platforms on which hoses or other items may be stowed fortransporting when not in use. One hose tray (166) is on the right sideof the exemplary trailer (100), which is depicted in FIG. 2. The otherhose tray (not shown) is on the left side of the exemplary trailer (100)and is not visible in FIG. 2. The example of FIG. 2 clearly depicts howthe hose trays (166) are lower than the front section underside (108) ofthe tank (102). As previously mentioned, this configuration allows atruck operator to easily access the hose tray (166) at the level of theoperator's torso while standing on the ground, which is more convenientand safer than in traditional trailers in which the hose trays are oftenlocated at or above the operator's head.

The exemplary trailer (100) of FIG. 2 also includes rear walls (170) formounting rear signal indicators such as breaking and turning signallights. The rear walls (170) of FIG. 2 are fabricated from sheets ofmetal, but other materials, such as fiberglass or carbon-fiber, as willoccur to those of skill in the art may also be used. The rear walls(170) are aligned vertically with respect to the hose trays and connectto the rear ends (172) of the hose trays (166). The rear walls (170) inthe example of FIG. 2 extend downward toward ground level for a lengthsufficient to provide a mounting surface for the rear signal indicatorsand for a set of rear platform. One of skill in the art will recognize,however, that the length of the rear walls (170) may vary from oneembodiment to another and that the length depicted in FIG. 2 ordescribed with reference thereto is for explanation only and not forlimitation.

In the example of FIG. 2, the exemplary trailer (100) includes rearplatforms (174) extending horizontally from the rear walls (170). Therear platforms (174) of FIG. 2 are configured from a metal mesh to avoidthe accumulation of liquids and debris. In other embodiments, however,the rear platforms may be configured from metal plates withperforations, solid metal plates, or even other materials as will occurto those of skill in the art. In the example of FIG. 2, the rearplatforms (174) are configured lower than the hose trays (166). Theconfiguration depicted in FIG. 2 facilitates the ability of a truckoperator to step up on the rear platforms (174) without the assistanceof a ladder or additional steps. From the rear platforms (174), thetruck operator may further scale the exemplary trailer (100) by steppingup on the hose trays (166) without the assistance of a ladder. Byeliminating the need for a ladder, the configuration of FIG. 2 improvessafety and convenience over traditional trailers. Such ladders or steps,however, may be provided for in some embodiments for additionalexpediency.

Previous tank trailer designs, including those designs disclosed inProvisional application Ser. No. 12/646,675 filed Dec. 23, 2009, andNon-Provisional application Ser. No. 12/924,071 filed Sep. 20, 2010,could be built using high tensile strength steel, specifically A572-65,exclusively for the tank trailer's front and rear sub-frame areas.Theoretically, one could substitute a thinner plate of high tensilestrength steel in lieu of a thicker normal tensile strength steel, suchas A36, without compromising structural integrity. The benefit thatwould be achieved is the reduction of overall weight of the tanktrailer. However, in practice this substitution does not work. Tanktrailers of the current embodiment were manufactured with the thinnersteel, it was found that while the steel was stronger, it was also morebrittle than the thicker normal tensile strength steel. This brittlenature of the thinner plates of high tensile strength steel caused thesteel plates to crack and split when put under excessive force, such aswhen the plate is being machined with a brake press.

To overcome the weakness of thinner high tensile strength steel, thepresent application achieves a better result by using thicker normaltensile strength steel, such as A36. To offset the additional weight ofusing a thicker and heavier plate of steel, the components produced fromthe thicker, heavier plate of steel can be 1) reducing the overall sizeof the component; 2) re-shaping the component; 3) removing excessivematerial from the component (holes, dimples, ovals, notched corners)and/or 4) removing the component from the design altogether. The presentdesign achieves this weight reduction through the above methods whileusing thicker normal tensile strength steel while maintaining thestructural integrity of the sub-frame component areas.

Another improvement of the currently disclosed tank trailer overprevious tank trailer designs comes with the design and placement of acatwalk and guardrail assembly. Original designs such as those inProvisional application Ser. No. 12/646,675 filed Dec. 23, 2009, andNon-Provisional application Ser. No. 12/924,071 filed Sep. 20, 2010,included catwalk and associated guardrails that extended from the rearof the tank trailer towards the front of the trailer, usually thesecatwalks and associated guardrails were approximately 28 feet in length,this approximately length was chosen for these previous designs as thecurvature of the vessel or tank made it prohibitive to extend the lengthany farther. Additionally, the previous designs had to include catwalksand associated guardrails that were shorter than the overall length ofthe tank trailer because of the weight limitations suffered by theseprevious tank trailer designs. This lack of a full length catwalk andassociated guardrails imposed hardships and hazards to the users of thetank trailer, as routine maintenance of the vessel or tank becomesextremely difficult without a normal catwalk and guardrail assembly,especially in wet or icy conditions.

The present application and disclosure over comes these previousshortfalls by extending the catwalk and guardrail assembliessubstantially the full length of the tank trailer. To compensate for theadditional weight of a full length cat walk, the present disclosure andcertain embodiments of the present application can do one or more of thefollowing actions to achieve this reduction in weight: 1) lowering theoverall height of the guardrails, 2) removing one or more horizontalcrosspieces, 3) reducing the size of the kick plate, and/or 4)redesigning the catwalk supports and using a thinner and lighter weightconstruction material.

Another often-fought issue with previous trailer designs is that ofbridging weight. Federal, state, and local laws, regulations andordinances require certain weights and length guidelines. Somejurisdictions allow for overweight load permits. Previous tank trailerdesigns failed to meet the bridging weight guidelines when loaded withcargo. As an example, the gross weight limit could be 84,000 poundsbeing distributed as 37,400 pounds on the trailer tandem, 37,400 poundson the truck drive axles, and 13,200 pounds on the truck steer axle. Thegross vehicle weight under this scenario should not exceed 84,000pounds. In addition to the overall weight limit, the particular axlesmust distribute as outlined above so that at any point the weight limitsare not exceeded for a certain axle and/or section of the tank trailerand tractor.

Ways of overcoming previous tank trailer failings, such as achieving alegal bridging weight, include increasing the diameter of the vessel ortank and installing dummy or hollow compartments in the rear half of thevessel or tank. This in theory displaces a certain volume of fluid (ordry cargo) and its associated weight from residing above the rear tandemaxle thus balancing the load to allow for a legal bridging weight. Caremust be taken not to overly enlarge the size or volume of the vessel ortank as it can lead to a failure point and be structurally unsound.

As an example, a tank trailer was manufactured to incorporate a partialdummy compartment in the rear portion of the vessel to produce a mainportion of the vessel for storage of cargo and/or fluid and a voidwherein cargo and/or fluid would not be stored in order to gain weightdistribution advantages. The walls of the dummy compartment werecomposed of ¼″ steel and internally braced with ¼″×2″×2″ angle iron. Thedummy compartment was designed as a half cylinder and was attached viawelds to the inner surface of the cylindrical vessel, see FIG. 2A for anexemplary embodiment of the partition (180) from FIG. 2. It can beappreciated that in FIG. 2A, the forward vertical wall (201) is asemi-circle with a radius that is half the internal diameter of thevessel. The forward vertical wall (201) is adjoined to the lower floor(202), through means known in the art such as welding or fasteners thatprovide a seal to prevent leaks through the adjoining seam. Thiscombination of the forward vertical wall (201) and lower floor (202) isthen affixed to the inner surface of the vessel, preferably over therear axle, but may of course be positioned at the front of the vessel.The combined forward vertical wall (201) and lower floor (202) arepositioned as such to create a void in the upper, rear portion of thevessel, wherein upper edge (203) adjoins the inner circumferentialsurface of the vessel, side edges (205) adjoin the inner side surfaces,preferably at the midpoint of the vessel's vertical height, and rearedge (204) adjoins the rear inner surface of the vessel. This designallows flowable product to extend the full length of the vessel,including over the rear tandem axles, until the product reaches a depthexceeding half the height of the vessel wherein the product would bedisplaced by the half cylinder dummy compartment leaving a void abovethe rear tandem axle. See FIG. 2A. In real world test and applicationsof the example tank trailer, the flat surfaces of the dummy compartmentdid not withstand the pressures, both positive and negative, applied tothe vessel during normal operating procedures. When a pressure wasapplied to the vessel, it caused the flat surfaces of the dummycompartment to flex, often as much as one to two inches of flex. Thiscontinued flexing when under pressure resulted in the angle ironsupports breaking in half, weld seams splitting, and tearing of thevessel wall itself. The failing of the dummy compartment of the currentexample failing resulted in even further issues such as the need toextricate leaked fluid and/or cargo from the dummy compartment, whichwas inaccessible in the above example. To overcome these deficienciesthe next iteration included internal reinforcements, such as verticalsupports (210) and/or horizontal bracings (212) to prevent the flatsurfaces from flexing as well as drain couplings (213) and plugs (notshown) to aid in the removal of leaked fluid and/or cargo from the dummycompartment in the event the contents leaked through a breach in thedummy compartment, as shown in FIG. 2A.

The results of the above mentioned improvements to the structure of thedummy compartment in tests revealed that the flat surfaces has a reducedtendency to flex, but this new rigidity transferred additional stressesto the vessel walls above the flat surfaces. After a period of time,these new stresses would result in one or more failures of the vesselwall leading to an external breach and leak of the vessel itself causinga loss of product (fluid and/or cargo), environmental damage, damage tothe tank trailer, among many other potential problems. It was discoveredthat in addition to the stress induced breaches that the internalcompartment design had a basic flaw: it had no factor or benefit if thetank trailer was not fully loaded. This version of the tank trailer madean assumption that the tank trailer vessel would be full withapproximately 130 BBL (5460 U.S. gallons) of product (fluid and/orcargo). By blocking or introducing the dummy compartment to make a voidin the rear portion of the vessel having a volume of approximately 500U.S. gallons one can shift the tank trailer's center of gravity forwardthus reducing the weight on the rear axle(s) and allowing for a legalweight. However, this scenario only worked when the product weighed lessthan 9.5 pounds per U.S. gallon. Many operators haul drilling mud, amongother known fluids, with a weight in excess of 9.5 pounds per U.S.gallon, sometimes even more than 17 pounds per U.S. gallon. When thissituation occurs, the operators will only haul a limited volume ofproduct so as not to exceed the overall weight limits of 84,000 pounds.The circumstance of loading product that was heavier than 9.5 pounds pergallon results in having the same initial problem sought to be overcomewith the half cylinder dummy compartment, too much weight over the reartandem axles causing the tank trailer to fail the bridging and weightrequirements even when under the maximum overall weight limits.

FIG. 2B shows a preferred embodiment of the partition (180) from FIG. 2,wherein the partition (180) is embodied as a substantially circular disc(220). The edge (221) is affixed to the inner surface of the vessel (notshown) through means known in the art, such as, welding or fasteners, sothat flowable product is not allowed through the seam between edge (221)and the inner surface of the vessel (not shown). In a preferredembodiment the interior diameter of the vessel was 64 inches, anotherpreferred embodiment had an internal diameter of 67 inches, as such thediameter of the substantially circular disc (220) had a substantiallymatching diameter and is then fixedly attached, via welding, 30 to 33inches, respectively, from the rear of the vessel. This placement andshape of the partition (180) provides a void in the rear portion of thevessel, preferably above the rear axle, thus achieving a proper bridgingweight, as described herein. It should be understood that the internaland/or external geometry of the vessel and the partition (180) can takemyriad shapes or configurations, such as rhomboids, ovals, or circles,and that the preferred embodiment is for illustration and notlimitation.

As shown in exemplary FIGS. 1 and 2, an example of a low-profile tanktrailer built in accordance with the accompanying disclosure lowered theindustry standard overall height from approximately 116 inches to 96inches, a reduction of 20 inches or 17%. The benefits realized from thisdisclosure include improved driver visibility around and over the top ofthe low-profile tank trailer, as well as reducing wind drag. The examplelow-profile tank trailer built in accordance with the accompanyingdisclosure also lowered the center of gravity, over the industrystandard, from 86 inches to 62 inches, a reduction of 24 inches or 28%.Just one of the benefits realized from this new low-profile disclosureis a less “top-heavy” tank trailer and thereby less prone to roll overincidents. The axle width of an example low-profile tank trailer builtin accordance with the accompanying disclosure includes an axle width of77.5 inches to widen the tank trailer to the maximum legal width of 102inches. The benefit realized through this widening of the tank trailerframe and base causes an improved stability for the tank trailer. Due tothe widened frame and lowered center of gravity, the force necessary tocause a roll-over of the tank trailer is significantly increased,thereby reducing the possibility of a roll-over. Other inclusions in theexample low-profile tank trailer includes relief valves such as 1.5 inchvacuum relief, 2 inch pressure relief both located on the front and topof the vessel body. Additional relief valves include a 2 inch pressurerelief line (blowdown) at the rear of the vessel body as well as a 2.5inch +30/−30 liquid filled pressure gauge. Further inclusions that canbe incorporated into a low-profile tank trailer consistent with thepresent disclosure include: manways, such as a 20 inch domed stylemanway with plated swing bolts and wing nuts; shut-off valves, such asan 8 inch stainless primary and 10 gallon secondary (moisture trap);lighting components, such as full DOT sealed LED lights, junction boxes,overhead work lights and switches located at various points on thelow-profile tank trailer; sight glass, such as a 1.5 inch OD acrylictube installed in the rear head of the tank trailer, 1.5 inch shutoffball valves, and a ¾ inch drain. A top load line can also be included toreduce loading time through the elimination of head pressure andelimination of a backing trailer to supply in some cases and alsoreduces the length of hoses for hookups.

For further explanation of the internal structural supports that enhancethe structural integrity of the frameless, self-supporting tank (102) inthe example of FIG. 2, FIG. 3 sets forth a drawing illustrating across-section of a top orthogonal view of the frameless, self-supportingtank (102) in the exemplary low-profile tank trailer according toembodiments of the present invention at the midpoint of the tank (102).

The tank (102) in the example of FIG. 3 has a rear section (104), afront section (106), and an intervening section (105) connecting therear section (104) and the front section (106). Although not depicted inthe view of FIG. 3, the front section (106) has a front sectionunderside (not shown), and the rear section (104) has a rear sectionunderside (not shown). The rear section underside is lower than thefront section underside. Accordingly, the center of gravity for the rearsection (104) is lower than the center of gravity for the front section(106). The front section (106) connects to the intervening section (105)at seam (134 a), and the intervening section (105) connects to the rearsection (104) at seam (134 b).

In the example of FIG. 3, the tank (102) includes a plurality ofstiffener rings (130). Each stiffener ring (130) of FIG. 3 is mountedalong an exterior perimeter of the tank (102) to reinforce the tank(102). The exterior perimeter of the tank (102) in FIG. 3 is thecircumference along the outside surface of the tank wall (196). In theexample of FIG. 3, stiffener rings (130 c, 130 d) are mounted adjacentto the seam (134 a) formed between the front section (106) and theintervening section (105) of the tank (102). In addition, stiffener ring(130 f) is mounted adjacent to the seam (134 b) formed between theintervening section (105) and the rear section (104) of the tank (102).Having stiffener rings or other structural enhancers adjacent to theseams (134) of FIG. 3 strengthens the structural integrity of the tank(102) at those seams (134).

The tank (102) in the example of FIG. 3 also includes two baffles (136)for dampening the movement of the flowable material throughout the tank(102), but only one baffle (136 a) is visible. Each baffle (136) of FIG.3 is mounted along an interior perimeter of the tank (102) and spans aninterior region of the tank (102). The interior perimeter of the tank(102) in FIG. 3 is the circumference along the inner surface of the tankwall. In FIG. 3, baffle (136 a) is mounted adjacent to seam (134 b)formed between the intervening section (105) and the rear section (104)of the tank (102). Similar to the stiffener rings, having the baffle(136 b) adjacent to the seam (134 b) of FIG. 3 strengthens thestructural integrity of the tank (102) at that seam (134 b).

To further reinforce the structural integrity of the tank (102) in theexample of FIG. 3, the tank (102) includes two gussets (140). A gussetis a plate extending vertically away from the surface to which it ismounted and provides structural support to that surface on which it ismounted. In the example of FIG. 3, each gusset (140) is mounted to abottom interior portion of the tank (102) and extends horizontally alongthe tank (102) as a single piece from the front section (106) into therear section (104) to reinforce the tank (102). The gussets (140) ofFIG. 3 are formed from a single piece of material such as, for example,metal because the structure formed from a single piece is oftenstructurally stronger than a structure composed of multiple pieces fusedtogether through welding or some other method. Each of the gussets (140)of FIG. 3 is made from a single piece of metal, typically steel, that iscut to fit along the bottom interior portion of the tank (102). Othermaterials or methods of making gussets useful in low-profile trailersaccording to embodiments of the present invention as will occur to thoseof skill in the art may also be useful.

In the example of FIG. 3, the gussets (140) do not extend along anentire length of the rear section (104). Rather, the gussets (140) onlyextend into the rear section (104) as far as the baffle (136 a) that ismounted adjacent to the seam (134 b) between sections (104, 105). Due tothe fabrications techniques used to mount the gussets (140) to the tank(102), a point of weakness in the structure of the tank (102) is createdwherever the gussets (140) terminate along the length of the tank (102).To reinforce the tank (102) at the point of weakness that is created bythe gussets (140), the gussets (140) of FIG. 3 terminate at the baffle(136 a), which provides structural reinforcement for the tank (102)generally and at the point that the gussets (140) terminate in the rearsection (104). To reinforce the tank (102) at the point where thegussets (140) terminate in the front section (106) of the tank (102),the tank (102) includes a stiffener ring (130 b) at the location wherethe gussets (140) begins extending from the front section (106) to therear section (104).

While the exemplary tank (102) in the example of FIG. 3 includes the useof stiffener rings, baffles, and gussets, one of skill in the art willrecognize that the use of these three components is for explanation, notfor limitation. Other low-profile tank trailers according to embodimentsof the present invention may or may not use any or all of thesestructural enhancements. Still further, other internal structuralenhancements as will occur to those of skill in the art may also beuseful such as, for example, cross-bar supports.

For further explanation regarding the placement of the gussets (140) inthe exemplary tank (102) of FIG. 3, FIG. 4 sets forth a drawingillustrating a right orthogonal view of the frameless, self-supportingtank (102) in the exemplary low-profile tank trailer according toembodiments of the present invention. FIG. 4 shows a cut-away of thetank (102) to reveal the gusset (140 b). The gusset (140 b) of FIG. 4 ismounted to a bottom interior portion of the tank (102) and extendshorizontally along the tank (102) as a single piece from the frontsection (106) into the rear section (104) to reinforce the tank (102).In the example of FIG. 4, the gusset (140 b) does not extend along anentire length of the rear section (104). Rather, the gusset (140 b) onlyextends into the rear section (104) as far as the baffle (136 a) that ismounted adjacent to the seam (134 b) between sections (104, 105).

For further explanation of the exemplary tank trailer (100) according toembodiments of the present invention, FIG. 5 sets forth a drawingillustrating a rear orthogonal view of the exemplary low-profile tanktrailer (100) according to embodiments of the present invention

FIG. 5 depicts the hose trays (166) mounted longitudinally along thebottom, lateral portions of the rear section (104). The hose trays (166)of FIG. 5 are mounted lower than the underside of the front section,which allows a truck operator to easily access the hose trays (166) atthe level of the operator's torso, rather than the more inconvenient anddangerous location of at or above the operator's head as withtraditional trailers. In the example of FIG. 5, each hose tray (166) isformed from one or more metal sheets configured at substantially rightangles—that is, approximately ninety degrees. Forming the hose trays(166) using substantially right angles reduces the bending, welding, orother fabrication technique required to configure a hose tray from metalsheets. The hose trays (166) depicted in FIG. 5 are configured usingfour right angles. Specifically, the hose tray (166 b) is formed from asheet that extends from the tank (102) to form a surface on which thehoses or other items rest. The sheet is then bent ninety-degreescounter-clockwise upward followed by three additional bends ofninety-degrees clockwise to form a lip and outside edge for the hosetray (166 b). Similarly, the hose tray (166 a) is formed from a sheetthat extends from the tank (102) to form a surface on which the hoses orother items rest. The sheet is then bent ninety-degrees clockwise upwardfollowed by three additional bends of ninety-degrees counter-clockwiseto form a lip and outside edge for the hose tray (166 a). One of skillin the art will recognize, however, that the configuration of the hosetrays (166) in the example of FIG. 5 and as shown in the other Figuresare for explanation only, not for limitation. Other configurations usingsubstantially right angles may also be useful in low-profile tanktrailers according to embodiments of the present invention.

FIG. 5 also depicts the rear walls (170) of the exemplary trailer (100).The rear walls (170) of FIG. 5 include mounting sockets for mountingrear signal indicators such as breaking and turning signal lights. Therear walls (170) of FIG. 5 are fabricated from sheets of metal, butother materials, such as fiberglass or carbon-fiber, as will occur tothose of skill in the art may also be used. The rear walls (170) arealigned vertically with respect to the hose trays (166) and extenddownward from the rear ends of the hose trays (166).

In the example of FIG. 5, the exemplary trailer (100) includes rearplatforms (174) extending horizontally from the rear walls (170). Asmentioned above, the rear platforms (174) of FIG. 5 are configured froma metal mesh to avoid the accumulation of liquids and debris, but suchplatforms (174) may be configured from metal plates with perforations,solid metal plates, or even other materials as will occur to those ofskill in the art. In the example of FIG. 5, the rear platforms (174) areconfigured lower than the hose trays (166). The configuration depictedin FIG. 5 facilitates the ability of a truck operator to step up on therear platforms (174) without the assistance of a ladder or additionalsteps.

In addition to the tank's overall shape, the exemplary low-profile tanktrailer (100) described herein utilizes a low-ride suspension andlow-profile tires to lower the trailer's center of gravity when comparedto traditional tank trailers. The low-profile tank trailer (100) of FIG.5 includes a low-ride suspension (112) that connects to the tank (102)through a tank substructure (158). The tank substructure (158) ismounted on top of the suspension (112), and in turn, the rear section(104) of the tank (102) is mounted to the tank substructure (158).

The low-profile tank trailer (100) of FIG. 5 also includes low-profiletires (114) operatively connected to the trailer suspension (112)through axle (200). To allow the tank (102) to rest as low as possiblein the space between the tires (114), the axle (200) of FIG. 5 isgenerally the widest commercially available axle that complies with theregulations promulgated by the various authorities governing the widthof trailers using the highway system. Such agencies may include astate's or federal government's department of transportation, publicsafety, highway administration, or any other such agency as will occurto those of skill in the art.

In the example of FIG. 5, the trailer suspension (112) includes asuspension frame (160) having a width that substantially matches themaximum width that provides a minimum clearance required for the tires(114). The minimum clearance required for the tires (114) is the minimumdistance from any other structure on the trailer that the tires (114)should be operated. Typically, this distance is specified by the tiremanufacturer but may be set by a governmental or other agency regulatingsuch distances. By maximizing the width of the suspension (112), thetank substructure (158) is made wider, and the tank (102) is permittedto sit lower on the trailer (100), thereby lowering the trailer's centerof gravity. In addition to ensuring the trailer suspension (112) is assubstantially wide as possible without violating the minimum clearanceneeded for the tires (114), the suspension (112) is also configured toaccommodate minimum clearances required for the axle (200).

The exemplary tank trailer depicted in FIGS. 1-5 is a vacuum trailerused to transport liquids. Accordingly, the tank of the exemplarytrailer of FIGS. 1-5 is enclosed for containing such liquids. That is,all the points of ingress or egress into the space within the tank areblocked from the environment outside the tank by covers, valves, hoses,or the like so that the tank's contents are not exposed to theenvironment surrounding the tank. One of skill in the art, however, willrecognize that the depiction of the enclosed tank in FIGS. 1-5 is forexplanation only and not for limitation. In other embodiments accordingto the present invention, a tank may be open to the environment abovethe tank. For further explanation, therefore, FIG. 6 sets forth adrawing illustrating a left perspective view of another exemplarylow-profile tank trailer (600) for transporting flowable materialaccording to embodiments of the present invention.

The exemplary tank trailer (600) of FIG. 6 includes a low-profile tank(602) that is open to the environment above the tank (602). Thelow-profile tank (602) in the example of FIG. 6 has a rear section(604), a front section (608), and a transitional section (606)connecting the rear section (604) and the front section (608) such thatflowable material can flow among the sections (604, 606, 608). In FIG.6, the front section (608) has a diameter smaller than the diameter ofthe rear section (604), and the rear section (604) has a lower center ofgravity than the center of gravity for the front section (608). The topside of the sections (604, 606, 608) are collinearly aligned, and thefront section (608) and the transitional section (606) are framelessunderneath. In FIG. 6, a trailer suspension is operatively connected tothe rear section (604).

In the example of FIG. 6, the tank (602) is open to the environmentabove the tank (602) along the entire length of the tank (602). Thisopening allows the tank trailer (600) to be conveniently filled withflowable material from above the trailer (600). One of skill in the artwill recognize that an open tank may be advantageous given that manytypes of flowable material such as, for example, gravel or sand, may bemore readily loaded into the top of an open tank than through a port inan enclosed tank. Although the opening in the tank (602) of FIG. 6extends along the entire length of the tank (602), such an embodiment isfor explanation only, not for limitation. In other embodiments, theopening in the tank may only extend a portion of the tank's length.Still further, there may be multiple places along the top of a tankuseful in trailers according to embodiments of the present inventionthat open the tank to the environment above the tank.

Based on the exemplary embodiment depicted in and described withreference to FIG. 6, one of skill in the art will recognize thatexemplary trailers according to embodiments of the present invention arenot limited to vacuum trailers. Other types of trailers may also beconfigured in accordance with embodiments of the present invention. Suchtank trailers may include insulated trailers, hauling trailers, cargotrailers, or any other type of trailer having a configuration inaccordance with embodiments of the present invention as will occur tothose of skill in the art.

FIGS. 1-6 depict tanks useful in an exemplary low-profile tank traileraccording to embodiments of the present invention that have circularcross-sections that vary in size along the length of the tank. One ofordinary skill in the art, however, will recognize that tanks used inlow-profile tank trailers according to embodiments of the presentinvention may have cross-sections configured in a variety of shapes,including elliptical, rectangular, triangular, and so on. Still further,the shape of the cross-sections for tanks of trailers according toembodiments of the present invention may vary along the length of thetrailer.

For further explanation, FIG. 7 sets forth a drawing illustrating aright perspective view of another exemplary low-profile tank trailer fortransporting flowable material according to embodiments of the presentinvention. The exemplary tank trailer (700) of FIG. 7 includes alow-profile tank (702) that has a generally rectangular cross-sectionand is open to the environment above the tank (702). The low-profiletank (702) in the example of FIG. 7 has a rear section (704), a frontsection (708), and a transitional section (706) connecting the rearsection (704) and the front section (708) such that flowable materialcan flow among the sections (704, 706, 708). In FIG. 7, the frontsection (708) has a circumference smaller than the circumference of therear section (704), and the rear section (704) has a lower center ofgravity than the center of gravity for the front section (708). The topside of the sections (704, 706, 708) are collinearly aligned, and thefront section (708) and the transitional section (706) are framelessunderneath. In FIG. 7, a trailer suspension is operatively connected tothe rear section (704).

While certain exemplary embodiments have been described in details andshown in the accompanying drawings, it is to be understood that suchembodiments are merely illustrative of and not devised without departingfrom the basic scope thereof, which is determined by the claims thatfollow.

We claim:
 1. A tank trailer for transporting a flowable materialcomprising: a vessel having three portions, a front portion, atransitional portion, and a rear portion, wherein the front portion hasa first internal diameter, the rear portion has a second internaldiameter, and the transitional portion has an third internal diameter inbetween the sizes of the first and second internal diameters, whereinthe rear portion has an inner surface; a rear suspension fixture fixedlyattached to the rear portion of the vessel; a rear axle fixedly attachedto said suspension; a valve for ingress of flowable materialcommunicating with an interior of the vessel; an exit valve for egressof flowable material from the interior of the vessel; and a kingpinfixedly attached for attaching said tank trailer to a truck rig.
 2. Thetank trailer of claim 1, wherein the rear axle comprises a dual axlefurther comprising low-profile wheels and tires.
 3. The tank trailer ofclaim 1, wherein the rear suspension fixture is fixedly attached to aframe, which is fixedly attached to the rear portion of the vessel. 4.The tank trailer of claim 1, wherein the rear portion of the vesselfurther comprises a partition, said partition having an outer edgefixedly attached to the inner surface of the rear portion of the vesselfor creating a void between a rear wall of the rear partition wherein noflowable material can enter said void.
 5. The tank trailer of claim 1,wherein the rear portion of the vessel further comprises: a partition,said partition comprising a first vertical portion and a secondhorizontal portion; the first vertical portion having a first edge thatfixedly adjoins a partial portion of the inner surface of said rearportion, and a second edge; the second horizontal portion having a frontedge, a rear edge, and side edges; said side edges fixedly adjoin asubstantially horizontal portion of the inner surface of the rearportion, the read edge that fixedly adjoins an rear wall of the rearportion; the second edge of first vertical portion fixedly adjoins thefront edge of the second horizontal portion.
 6. The tank trailer ofclaim 5, wherein the first and second edges of the first verticalportion and the front, rear, and side edges of the second horizontalportions are fixedly adjoined through a weld.
 7. The tank trailer ofclaim 1, wherein the valve is a side load valve for the ingress offlowable material.
 8. The tank trailer of claim 5 wherein the valve is aside load valve for the ingress of flowable material.
 9. The tanktrailer of claim 1, wherein the valve is a top load valve for theingress of flowable material.
 10. The tank trailer of claim 5, whereinthe valve is a top load valve for the ingress of flowable material. 11.The tank trailer of claim 1, wherein the rear portion of the vesselfurther comprises a partition, said partition comprising a firstvertical portion having a first edge, wherein said partition fixedlyadjoins said inner surface of the vessel with said first edge.
 12. Thetank trailer of claim 11, wherein the partition is substantiallycircular.
 13. The tank trailer of claim 12, wherein the edge of thesubstantially circular partition is fixedly adjoined to the innersurface of said vessel through a weld.
 14. The tank trailer of claim 1,wherein the rear portion further comprises a plurality of bafflesfixedly adjoining the inner surface of the vessel for the dampening ofmovement of said flowable material during transport of said flowablematerial.
 15. The tank trailer of claim 5, wherein the rear portionfurther comprises a plurality of baffles fixedly adjoining the innersurface of the vessel for the dampening of movement of said flowablematerial during transport of said flowable material.
 16. The tanktrailer of claim 13, wherein the rear portion further comprises aplurality of baffles fixedly adjoining the inner surface of the vesselfor the dampening of movement of said flowable material during transportof said flowable material.
 17. A tank trailer for transporting aflowable material comprising: a vessel, said vessel comprising asubstantially cylindrical body having an outer surface, a forward end, arearward end and an inner surface, forming an interior portion of thevessel; a frame fixedly attached to a lower portion of the outer surfaceof said vessel at the rearward end of said vessel; a suspension fixture,said suspension fixture comprising an axle and a plurality of wheels,said suspension fixture being fixedly attached to said frame; a king pinfor attaching said tank trailer to a truck rig, said king pin fixedlyattached to the outer surface of said vessel at the forward end of saidvessel; a partition for blocking the flow of said flowable materialwithin the interior portion of the vessel, said partition comprising afirst surface, a second surface, and an edge, said first surface facestowards the forward end of the vessel, said second surfaces faces therearward end of the vessel, said edge fixedly adjoining said innersurface of said vessel; a valve fixedly attached to the outer surface ofsaid vessel and communicating with the interior of said vessel foringress of said flowable material into the interior of said vessel; and;an exit valve fixedly attached to the outer surface of said vessel andcommunicating with the interior of said vessel for egress of saidflowable material away from the interior of said vessel.
 18. The tanktrailer of claim 17 further comprising: a walkway fixedly attached tothe outer surface of said vessel extending from the forward end of thevessel to the rearward end of the vessel; a hose mount for capturing ahose during transport of said tank trailer, said hose mount adjoiningthe outer surface of said vessel.
 19. The tank trailer of claim 18,wherein the valve is a side load valve for ingress of said flowablematerial.
 20. The tank trailer of claim 19, wherein said interior ofsaid vessel has a volume of at least one hundred-thirty barrels offlowable material; wherein said truck rig comprises a truck steer axleand a truck tandem axle; wherein said tank trailer and said truck rigtogether have a gross weight that does not exceed 84,000 pounds, thegross weight distributed such that no more than 12,600 pounds is appliedto the truck steer axle, no more than 35,700 pounds is applied to thetruck tandem axle, and no more than 35,700 pounds is applied to the axleof the tank trailer suspension fixture; wherein said partition ispositioned within the interior of said vessel so as create a cavitysubstantially above said tank trailer suspension fixture.